1. Field of the Invention
The present invention relates to archery equipment in which the force to be imparted to an arrow is held by the archer and more particularly to a bow and bowstring release mechanism which optimize the force exerted on the arrow upon release.
2. Description of the Prior Art
Bow designers have from ancient times sought to increase the speed at which an arrow is launched thereby improving the trajectory, range and destructive power of the arrow.
The efforts of the designers have resulted in a progression of bows from the conventional long bow to the recurved bow and, in more recent times, to the compound bow. To shoot an arrow each bow must be held at arms length with one hand while the other hand and arm pulls the bowstring from its resting position to its full draw position. The force exerted on the bowstring by the archer is commonly referred to as the draw weight. Once the bowstring is in the full draw position, the bow must be held in a steady position while the arrow is aimed at a desired target and then released. The limiting factor on draw weight is the strength of the archer's back muscles and particularly the strength of the back muscles associated with the pulling arm.
The compound bow utilizes eccentric wheels or pulleys mounted on the ends of the bow limbs and a pair of cables in addition to the bowstring connected between the wheels to increase the stored energy (and exit velocity) imparted to an arrow over that available with a recurved bow. The compound bow accomplishes this by providing a peak draw weight intermediate the resting and full draw positions and a lower draw weight at the full draw position to increase steadiness while aiming and maximizing the total stored energy stored in the bow limbs. The difference between the peak draw weight and the full draw weight in percent is commonly referred to as let-off. As the let-off increases the full draw weight decreases as compared to the peak draw weight and visa versa. A compound bow with a let-off of say 40-50%, at full draw, may increase the exit velocity of an arrow from the bow by as much as 40% over a recurved bow having the same draw weight at the full draw position. However, the strength of the archer's back muscles associated with the pulling arm still limits the total draw weight which can be designed into the bow.
To accurately shoot an arrow it is necessary to provide a rest (or launcher) for the front of the arrow and a nocking point for the rear of the arrow near the middle of the string. The arrow rest and nocking point define the axis along which the arrow is accelerated from the bow (i.e. shooting axis). Conventional bows carry an arrow rest near the hand grip on the riser or central section. Such rests commonly contact the vanes, feathers or fletches (hereinafter "vanes") affixed to the rear of the arrow and may deflect the arrow either laterally (i.e. out of the true plane of movement of the bowstring) or vertically (i.e. up or down) or both. Since such deflections are inconsistent and unpredictable it is difficult for the archer to make allowances therefore.
The position of the arrow rest on the bow's central section and the draw length of the bow determines the minimum length of the arrow suitable for use with the bow. To shoot shorter (and stiffer) arrows it is necessary to position the arrow rest closer to the bowstring. However, the placement of the arrow rest must accommodate the movement of the bowstring to its post release position (i.e. beyond its resting position toward the central section) after the arrow has been released to prevent the bowstring from striking the arrow rest. This post release movement, which may amount to several inches, adds to the minimum length of an arrow suitable for use with any given bow.
Another problem encountered with conventional bows concerns the accurate alignment of the central bow section and its attendant arrow rest within the plane of the movement of the bowstring. To take the forearm of the arm holding the bow out of the path of the bowstring, it is necessary for the archer to roll or bend the arm and/or wrist. This creates a sideways moment or torque that tends to twist the central section of the bow and the arrow rest out of the plane of the moving bowstring. Many bows have a peep sights affixed to the bowstring and a bowsight with a vertical cross-hair (and horizontal range lines) affixed to the central section. However, the alignment of the peep sight with the vertical cross-hair and the target does not inform the archer that the central section is precisely aligned with the plane of movement of the bowstring. Some skilled archers may be able to compensate for such misalignment (most of the time) by aiming slightly to one side or the other of the desired target while holding the bow so that their forearms are in exactly the same position each time. Others try to shoot with the bow hand open to avoid torque. However, most archers cannot accomplish these feats consistently. This torque factor simply increases the skill level required to place arrows within a desired target at any given range.
Various approaches have been taken in the past to alleviate some of the above problems. To increase an arrow's exit velocity, compound bows have been constructed with increased peak draw weights and let-offs of the order of 30% or less. However, such bows are difficult to hold steady during the aiming process. Even with such decreased let-offs the strength of the archer's back muscles associated with the pulling arm remains the limiting factor on maximum draw weight and energy stored in the limbs.
The arrow rest/vane contact problem has been addressed primarily by building flexibility into the rest so that the portion of the rest in contact with the arrow will move out of the arrow's path (i.e., bend or rotate against a spring) when contacted by the vanes. In each case there is inherently some contact between the vanes and the arrow rest which causes some unwanted deflection of the arrow. See, for example, the arrow rests illustrated on pages 33-35 of the Spring 1988 edition of the Bowhunters Discount Warehouse Inc's catalogue of Wellsville, Pa. The flexibility built into conventional rests is also needed to accommodate flexing of the arrow shaft during acceleration (i.e. arrow paradox).
Another prior approach to the arrow rest/vane contact problem involves the use of a mechanism which attempts to sense the shock to the bow when the bowstring is released to move the arrow rest out of the way. However, this type of mechanism has proven unreliable in retracting the arrow rest at the proper time if at all. If the arrow rest is retracted too soon, the force of gravity will cause the front of the arrow to drop during the acceleration phase and change the desired shooting axis.
Various prior art patents have proposed solutions to some of the above problems. For example, U.S. Pat. No. 3,517,657 describes a sling shot type bow in which a rigid member such as a rod extends between a hand held central member and the bowstring in its full draw position. The archer can hold the remote end of the rod and an arrow release mechanism in the cocking hand to thereby relieve tension on the extended or aiming arm. This type of bow (similar to a cross-bow in operation) while perhaps relieving some pressure on the user's arms would not be tolerated in archery tournaments or by hunting regulations which require that the drawstring force be held by the archer. Furthermore, the maximum draw weight for such a bow is still limited by the strength of the archer's back muscles associated with the pulling arm. A device similar to that shown in the '657 patent (referred to as a vertically oriented crossbow) is described in U.S. Pat. No. 2,714,884. Another device for modifying a conventional bow so that it will shoot like a crossbow has been advertised by The Market Place of Freemont, Wis. on page 69 of the October, 1985 issue of Bow and Arrow.
U.S. Pat. Nos. 2,344,799 and 4,662,344 describe bows which use elastic bowstrings to propel the arrow. U.S. Pat. No. 4,787,361 describes a combination handgrip and forearm protector for bows for reducing the tendency of the bow to twist when the arrow is released. However, there is nothing in the described apparatus which allows the user to determine whether or not the central section of the bow and the arrow rest carried hereby is in fact twisted out of alignment.
U.S. Pat. No. 4,674,469 describes a bowstring release to be held in the hand of the pulling arm. A solenoid actuated by a finger on such hand may be used to release a sear from engagement with the bowstring.
A need exists for an archery apparatus in which (1) the maximum draw weight is optimized for a given archer for any given bow (i.e., longbow, recurved or compound bow), (2) the arrow rest is positioned adjacent the bowstring in its rest position to allow the use of shorter arrows, (3) the arrow rest is retracted at the proper time to eliminate interference with the flight of the arrow and (4) any misalignment of the central section of the bow can be detected and corrected by the archer.